Patent Application
20110139689
1. Field of the Invention
This invention resides in the field of preparative chromatography columns.
2. Description of the Prior Art
Preparative chromatography is a separation technique used to extract individual chemical species from mixtures of species for purposes of obtaining the individual species in sufficient quantity and purity to be used for therapeutic or other procedures. Preparative chromatography thus differs from analytical chromatography whose purpose is simply to determine the presence or concentration of particular components in the mixture or to determine the composition of the entire mixture. Preparative chromatography is used, for example, for purifying monoclonal antibodies and other proteins, as well as for purifying vaccines and any variety of peptides. Preparative chromatography is commonly performed by passing the source mixture through a packed column that will bind the species of interest, then eluting the bound species column with an elution buffer once all of the other components in the source mixture have passed through the column or have been washed out of the column with a wash buffer. The binding of the species of interest is achieved by any of a variety of interactions between the mobile phase (which includes the source mixture) and the stationary phase (the column packing). Examples of these interactions are ion-exchange chromatography, affinity chromatography, and liquid-liquid or partition chromatography.
Flow through a preparative chromatography column is generally in the axial direction, and the axial length of the column must be limited in order to avoid an excessive pressure drop through the column, since high pressure drops require a high mobile phase pump pressure, high power to drive the pump, or both. With columns of limited depth, however, the extraction of the species of interest at a rate that is commercially useful requires a column of large diameter. The typical preparative column thus has a diameter of at least several centimeters, and in some cases, a meter or more. Columns of large diameter present certain challenges, however, one of which is the difficulty in distributing the flow effectively across the width of the column. A uniform flow distribution is needed for good separation and resolving power and for maximal use of the column packing, and the larger the diameter the more difficult these are to achieve. Flow distributors are typically used at both ends of the column to address this problem. Another challenge, which arises particularly in columns that are arranged vertically with downward flow, is the difficulty of packing the column in a manner that produces a uniform packing density in the column. A poorly packed bed will contain void spaces that cause flow channeling which can likewise reduce the contact between the mobile and stationary phases and thereby reduce the resolving power. Void spaces can be eliminated by applying pressure to the packing, and a sliding piston, also referred to as an “adaptor,” which also contains flow distribution channels, is commonly used for this purpose. A piston applying high pressure to the packing, however, can lead to fracture or pulverization of portions of the packing material, particularly if the material is incompressible or fragile. The lowering of the adaptor must therefore be closely controlled to avoid such damage. Additionally, for those resins where packing is controlled by compressing the resin to a prescribed degree relative to its uncompressed state, the total amount of resin in the column, and hence the resin height, prior to compression must be known.
The present invention resides in a preparative chromatography column whose wall includes a strip of transparent material that functions as a sight glass through which the height, the density, or both, of the column packing can be monitored as the column is being loaded with the packing material. The transparent strip can also allow the position of the adaptor to be monitored as the adaptor is being lowered onto the packing. While the major portion of the column wall is typically constructed of steel or other opaque material, the monitoring strip is transparent to allow monitoring to be performed through the column wall from the exterior of the column.
These and other objects, features, and advantages of the invention will be apparent from the description that follows.
The strip of column wall occupied by the transparent material will at least have a component that is parallel to the longitudinal axis of the column. The strip can thus itself be parallel to the axis or it can be a spiral or otherwise angled with a tangential component and an axial component. For purposes of simplicity, a strip that is itself parallel to the column axis is preferred. The length of the strip in the axial direction can be equal to or less than the length of the column, provided that it has an axial length and position that brackets the range of bed heights that may be used in the column and that allows observation or detection of the adaptor position as it the adaptor approaches the bed.
Any transparent material that is rigid, that can withstand the column pressure, and that is inert to all liquids and other materials that will occupy the column, including biological fluids, wash buffers, and elution buffers, can be used for the monitoring strip. Preferred transparent materials are those that are also resistant to etching and other surface degradations that might reduce visibility. Examples of suitable materials are transparent polymers such as acrylic, polycarbonate, a styrenic polymer, a polyester, or a polyimide. Further examples are glass such as borosilicate glass, soda lime glass, lead glass, fused quartz, diamond, or sapphire. The strip can be plain or can have markings to indicate the height of the visualized packing or of the adaptor above the column floor.
The transparent strip is preferably mounted in the column wall in such a manner that the strip is sealed along its edges to prevent leakage around the strip of any fluids from the column interior. The strip is also preferably shaped and mounted in such a manner that the inner surface of the strip does not interfere with, or otherwise influence, either the distribution of packing material in the column or the flow of liquid through the column. The column itself is a cylinder, which term is used herein according to its dictionary definition to mean the surface created by a straight line moving parallel to a fixed straight line and intersecting a fixed planar closed curve. A right circular cylinder is one in which the closed curve is a circle and the fixed straight line is the axis of the circle or any line that is perpendicular to the plane of the circle. Thus, for a column that is a right circular cylinder, the inward-facing surface of the strip is preferably of a concave curvature to match that of the inner wall surface of the column.
Securement of the strip to the remainder of the column wall can be achieved by conventional means, although a preferred means is by providing the strip with a cross section in the form of a truncated wedge so that pressure from the column interior will force the edges of the strip against the contacting edges of the adjacent column wall to enhance the seal. Gasket materials can also be placed between the contacting edges to further enforce the seal. To compensate for any lessening of the column's structural integrity due to the inclusion of the transparent strip, a reinforcing flange or band can be placed around the outer surface of the column wall.
Monitoring of the column packing through the strip of transparent material can be performed by instrumentation, including machine detection, automated illumination and the detection of reflected or non-absorbed light, or by visual observation. Monitoring by visual observation is preferred.
The attached figures offer views of an example of a preparative chromatography column incorporating the features of the present invention.
Numerous variations on the structure and configuration shown in the Figures that are still within the scope of the invention will be apparent to those skilled in the chromatography art. For example, the column wall can contain two or more transparent strips positioned at different locations around the column circumference. Other examples will be readily apparent.
In the claims appended hereto, the term “a” or “an” is intended to mean “one or more.” The term “comprise” and variations thereof such as “comprises” and “comprising,” when preceding the recitation of a step or an element, are intended to mean that the addition of further steps or elements is optional and not excluded. All patents, patent applications, and published reference materials in general that are cited in this specification or added thereto subsequent to filing are incorporated herein by reference in their entirety. Any discrepancy between any reference material cited herein and an explicit teaching of this specification is intended to be resolved in favor of the teaching in this specification. This includes any discrepancy between an art-understood definition of a word or phrase and a definition explicitly provided in this specification of the same word or phrase.
This application claims the benefit of U.S. Provisional Patent Application No. 61/221,926, filed Jun. 30, 2010, the contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61221926 | Jun 2009 | US |
